Silicone in one breast, saline in the other?

I had a skin-sparing mastectomy last fall, R breast, and a tissue expander inflated to 450 mL. For my implant surgery (in a week from today), I plan to have a small implant in the L breast for symmetry / consistency. My plastic surgeon plans to use a silicone round implant for the R (mastectomy) side, and an inflatable round saline implant on the L side, under the muscle. The saline on the L side is so that, during surgery, it can be inflated to a size that best matches the R breast. She says it won’t feel any different. I’m not convinced this is the way to go. Is this a viable approach that plastic reconstruction surgeons use? Is there a better approach? Thank you for any information you can provide!